This application relates to materials with optical properties, and more specifically to single component polymeric frequency-doubling materials.
Materials which exhibit highly nonlinear optical characteristics of doubling or tripling the frequency of incident light are currently of great scientific and technological interest for use in optical telecommunications, optical signal processing and, ultimately, the construction of optical computers. Nonlinear optics is concerned with the interactions of electromagnetic fields in various media to produce new fields which may be altered in phase, frequency, or amplitude. Such media and their properties (their stability, ease of preparation, compatibility with microelectronic processing methods, adhesion, mechanical, and other properties) as well as their nonlinear optical properties will ultimately determine the technological utility of any possible application.
The use of inorganic materials, such as KH.sub.2 PO.sub.4, LiNbO.sub.3, or InSb, as NLO materials is being replaced by materials based upon conjugated .pi.-electron organic chromophores, substances which normally supply color to a substance; such organic chromophores promise superior performance and adaptability to the desired chemical functions. Organic (.pi.-electron) nonlinear optical materials characteristically have large non-resonant susceptibilities, ultrafast response times, low dielectric constants; high-damage thresholds and intrinsic tailorability. The nonlinear optical response exhibited by organic materials with such large delocalized .pi.-electron systems is in many cases, much better than that shown by inorganic materials.
When utilizing nonlinear chromophores within an organic matrix to attain second order nonlinearities (frequency doubling, second harmonic generation or, simply, SHG), the chromophore molecules must be in a specifically aligned orientation within the organic matrix for the frequency doubling effects. Some current organic chromophore systems involve dissolving the chromophore guest molecules in a suitable polymer host, heating the mixture above the glass transition temperature of a polymer (T.sub.g); the chromophore molecules are then orientated or "poled" by the use of an applied DC electric field and cooled. These materials are sometimes referred to as solid organic guest-host substrates. Several disadvantages with guest-host substrates have been noted. For example, there may be limited solubility of the chromophore in the host polymer, resulting in crystallization of the chromophore out of the polymer matrix and subsequent poor frequency coubling performance; instability of the polymer-chromophore mixture has been observed resulting in the leaching or vaporizing of the chromophore molecules from the host polymer, causing deterioration in frequency doubling performance; there may be mobility of the chromophore molecule within the host polymer matrix, allowing relaxation of the chromophore orientation and resulting in loss of second harmonic generation.